Screw/bolt extractor or left handed drill bit recommendations

[earl84]

I have an POS '97 Olds 88 that has a couple broken bolts on engine mounts that I have to pull the freakin' engine on and replace, cannot get to the bolts otherwise. Long story, don't ask.
So, I would like to have some QUALITY either bolt extractor kit or left hand drill bit recommendations. I've had the cheap ones, and been through the frustration of cheap tools. Think I'd learn by the age of 48, but noooooooo.
Don't necessarily need a whole set, just one or two sizes, the bolts are about 1/4 inch to 5/16 inch, but in metric, whatever that equivalent is. Anyone have some good luck with any that they can make a recommendation on?